This invention relates to a device for adjusting the backrest, particularly the lumbar support, of seats. The device preferably is intended for use with vehicle seats where, due to alternating g-forces in combination with periods of long duration of occupying the seat, an anatomically correct support for the back is desirable to prevent lingering back injuries.
It is previously known to provide vehicle seats with lumbar supports, which may consist of one or more belts located on the same level as the lumbar region of the back. These belts are adjustable in their stretching transversely to the seat back. the stretching in principle is effected by a screw-nut device. Another type of adjustable lumbar support comprises one or more inflatable cushions provided in the backrest. The pressure in the cushions is adjusted by one or more small hand pumps. In the first-mentioned type of lumbar support, the belts are loosened or stretched by the screw-nut device. In the second type of lumbar support, an amount of air is pumped into or discharged from the cushions to bring about a correct sitting position. Both types of lumbar supports thus require a relatively complicated adjusting process, which in turn implies that the user often carries out the adjusting in a negligent or careless manner and thereby fails to produce the effect desired of the relatively expensive seat.
The present invention yields a backrest adjusting device which per se is simple and renders its adjusting very simple, thereby increasing the efficiency of the seat.